1. Field
This invention relates to the field of transmitting systems, and more specifically, to an injection-locked differential oscillator transmission system.
2. Background
Power conservation is a critical concern for many transmitting systems known in the art. Power creates electromagnetic signals for transmission and is used by processors which receive the signals. Higher frequency signals require increased component power consumption. A signal created by a transmitter generally travels a path between the device that generates the signal and an antenna. While the signal does not need a high frequency along this path, most antennas which receive a communications signal for transmission to a receiving device only have the capability to transfer signals at a high frequency. Therefore the signal must be upconverted at some time prior to transmission.
An article published by the IEEE Journal of Solid-State Circuits in 2011, entitled “A Sub-100 μW MICS/ISM Band Transmitter Based on Injection-Locking and Frequency Multiplication”, authored by J. Pandey et al., is hereby incorporated by reference in its entirety for its teachings on the use of injection-locked frequency multiplication (ILFM) systems. An ILFM system uses a circuit assembly to delay conversion from low to high frequency for as long as possible in order to conserve power. In an ILFM system, a low frequency clock creates a “steady” signal with a constant amplitude. The clock is coupled to a frequency oscillator with multiple phase outputs. All of these outputs feed into a component called an edge combining power amplifier (ECPA). The ECPA uses digital logic to combine the waveform signals into a single high frequency signal. The output logic is based on the following expression:Output=AB+BC+CA, where A, B and C are outputs from the oscillator.
In an ILFM system, only the ECPA operates in high frequency. This reduces overall power consumption to about 90 μW.
A problem known in the art with the ILFM system is that it is limited to Frequency-Shift Keying (FSK) modulation and cannot perform On-Off Keying (OOK) modulation, Binary Phase-Shift Keying (BPSK) modulation or Quadrature Phase Shift Keying (QPSK) modulation. An FSK modulation requires a higher signal-to-noise ratio than OOK, BPSK, or QPSK modulation traveling the same distance.
Another problem known in the art with the ILFM system is that it does not provide bandwidth sufficient for many communications applications.
It is desirable to structurally modify an ILFM system known in the art so that it is enabled to perform OOK, BPSK and QPSK modulation over a wider bandwidth.